FIELD: data processing.
SUBSTANCE: invention relates to decoding images. An image decoding device performs bitstream decoding and comprises: a unit for decoding information on a significant sub-block, which indicates equality or inequality "0" of all values of difference coefficients related to the subunit; unit for decoding information on significant difference coefficient, indicating equality or inequality "0" value of difference coefficient; unit for decoding of differential coefficient value; and a context extraction unit which extracts the index and the context used to decode information on the significant difference coefficient of the difference coefficient, which is the decoding object, based on said index and the position of the difference coefficient being the decoding object in the sub-block being the decoding object; wherein the context extraction unit extracts mutually different indices when the information on the significant sub-block of the decoded sub-block being adjacent in the horizontal direction has a value of "1", and information on significant subunit of decoded sub-block, which is adjacent in vertical direction, has value "0", and when the information on the significant sub-block of the decoded sub-block which is adjacent in the horizontal direction is "0", and the information on the significant sub-block of the decoded sub-block which is adjacent in the vertical direction is "1"; and the context extraction unit extracts the context based on the position of the difference coefficient being the decoding object in the horizontal direction in the sub-block which is the decoding object, when the information on the significant sub-block of the decoded sub-block, which is adjacent in the horizontal direction, has value "0", and the information on the significant sub-block of the decoded sub-block, which is adjacent in the vertical direction, has value "1".
EFFECT: increase the efficiency of image decoding.
3 cl, 25 dwg
